Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$75.25	9.469%	$82.3754	$82.38	$82.40	$82.40
Purchase #2	$89.81	13.636%	$102.0565	$102.06	$102.05	$102.10
Purchase #3	$132.37	8.751%	$143.9537	$143.95	$143.95	$144.00
Purchase #4	$14.78	10.496%	$16.3313	$16.33	$16.35	$16.30
Purchase #5	$113.32	9.168%	$123.7092	$123.71	$123.70	$123.70
Purchase #6	$86.34	7.330%	$92.6687	$92.67	$92.65	$92.70
Purchase #7	$176.47	11.591%	$196.9246	$196.92	$196.90	$196.90
7 purchase totals =	$688.34		$758.0194	$758.02	$758.00	$758.10